An offset or indirect solid ink printer typically utilizes a series of rollers to fix solid ink to a print surface to form a printed image. In general, solid ink is loaded into a printer and then melted to produce liquid ink that is ejected onto an intermediate imaging member to form an ink image on the surface. In the offset print process, the intermediate imaging surface is frequently the surface of a rotating drum, belt, or band, often referred to as an imaging drum. Thereafter, print media, such as paper, is moved proximate the surface of the rotating intermediate imaging member in synchronization with the ink images formed on the surface of the imaging drum. The media surface is pressed against the surface of the rotating imaging member as the media passes through a nip formed between the rotating member and a transfix roller. The ink image is transferred and affixed to the print media by the pressure in the nip.
To address accumulation of ink on an imaging roller, offset solid ink printers often utilize a release agent (e.g., silicon oil) to aid in the clean release of the solid ink from the imaging drum to the print surface. The release agent is applied to the imaging surface before the ink is ejected to help reduce the likelihood of ink adhering to the imaging drum. In many offset solid ink printers, a release agent applicator remains in contact with a reservoir of the release agent and is selectively moved into contact with the imaging drum to apply the release agent. The applicator is then moved out of contact with the imaging drum so the ink image can be formed on the rotating surface and once the image is transferred to the media, the applicator is brought back into contact with the imaging surface to apply a fresh layer of release agent.
Because release agent is typically electrically insulating, and the release agent applicator is often made from an electrically insulating composition, such as urethane or other foam, friction between the release agent applicator and the imaging drum can cause a static charge to accumulate on the layer of release agent that is coating the release agent applicator. The static charge can accumulate to the point where the accumulated electro-motive force difference between the charged release agent and the imaging drum results in one or more drops of the release agent jumping from the release agent applicator to the imaging drum roller. These displaced drops of release agent onto the imaging drum may cause image quality defects.
Previous attempts at eliminating the issue of static charge accumulation on the release agent applicator surface include the use of a conductive urethane metering blade placed in contact with the release agent applicator to dissipate any accumulating charge, or utilizing a release agent applicator with a conductive surface. However, manufacturing a release agent applicator with a conductive surface has proven problematic, as such rollers often comprise a porous foam, which unevenly absorbs any conductive materials applied thereto. Such an uneven uptake produces an irregular ionic map on the finished surface of any such release agent applicator. The resulting applicator is incapable of dissipating the static charge buildup effectively.